Chance to Grow More Wheat Tillers
Late January to early February is the time to determine if the wheat crop has enough tillers to optimize yield. This is a very important decision. Apply N in January or February only if tiller densities are less than 50 tillers per square foot. If N is not needed, applying N in January or February results in increased risk of freeze damage, disease, lodging, and reduced yield. If tillering is low; however, an early application of N can help to stimulate further tiller development in the last few weeks before growth stage 30, resulting in higher yield and profit. The calendar date when wheat reaches growth stage 30 is influenced by variety, planting date, and environmental conditions. Early heading varieties can reach it in February. Late heading varieties may not reach growth stage 30 until mid-March. The following guidelines will help you decide whether to apply N in late January or early February.
A well-developed tiller is one stem with at least three leaves. If at the end of January or in the first week of February, wheat looks fully matted, then it is well on the way to being a potentially high yielding field. If wheat has about 100 well-developed tillers per square foot it should not have any N applied until growth stage 30. Wheat with a “medium” density stand with about 50 tillers per square foot, is well on the way to being a good yielding crop, and should not have any N applied until growth stage 30. If wheat has poor tiller development and only has about 20 tillers per square foot, then it has a low yield potential and needs more tillers to develop in February. It should have 50 to 70 pounds N fertilizer applied in late January or early February. A second N application should be made to finish this crop off at growth stage 30. Thin stands need timely weed management, but should not have 2,4-D applied because 2,4-D may inhibit tiller development. Growers also need to scout for cereal leaf beetles in April, as these insect pests are often attracted to thin wheat stands.
Wheat stands that are thicker but not as well developed may also need an early N application. Such a field will yield best with 40 to 50 pounds of N fertilizer applied in late January or early February and a second N application at growth stage 30.
To determine tiller density, count all the tillers that have at least three leaves in a yard of row. Do this in several places and take an average. Tiller density is then computed as follows:
Tillers per square foot =
(tillers per yard of row) X 4
(row width in inches)